Structural, Electrical and Optical Properties of CuO Thin Films Obtained by Reactive Magnetron Sputtering

Abstract

CuO thin films were produced by the method of reactive magnetron sputtering at direct current in a universal vacuum system Leybold-Heraeus L560 on glass substrates, the temperature of which was: 300 K and 523 K. The structural, electrical and optical properties for the obtained samples of CuO thin films were studied, namely: elemental composition, distribution of elements on the surface, which are part of these films, grain size, activation energy, optical band gap, refractive index, analysis of curves of transmission and reflection spectra for CuO thin films deposited on glass substrates. The elemental composition of the thin films and the surface morphology were performed using a scanning electron microscope (MIRA3 FEG, Tescan) equipped with a reflected electron detector (BSE) and an energy-dispersed X-ray detector (EDX). It was found that the grain size for films obtained at a lower substrate temperature D is ~ 16 nm, and for films obtained at a higher temperature - D ~ 26 nm. On the diffractograms of CuO thin films, a higher peak intensity is observed for thin films obtained at higher CuO no. 2 substrate temperatures, which may be due to better structural perfection of thin films and larger grain size. From the study of electrical properties, it was found that the temperature dependences of the electrical resistance for CuO thin films have a semiconductor character, ie the resistance decreases with increasing T. The surface resistance of the films was measured by the four-probe method: no. 1- ρ = 18,69 kΩ/¨, sample no. 2 – ρ = 5,96 kΩ/¨. Based on independent measurements of the reflection and transmission coefficients, the optical band gap was determined for the two samples by extrapolation of the rectilinear section of the curve (αhν)² = f (hv) to the hv axis. For the sample CuO №1 E_g^op = 1.62 eV; for the sample CuO no. 2 E_g^op = 1.65 eV. For CuO no. 2 thin films, the envelope method was also used to determine the basic optical coefficients E_g^op = 1.72 eV, and the obtained E_g^op values determined by the two methods correlate well with each other.